In order to prevent an increase in temperature of an airframe due to incidence of solar light, a surface of an artificial satellite or a rocket used in space is coated with a thermal-control material having a function of reflecting the solar light and radiating thermal energy of the solar light to space.
A flexible thermal-control material, a so-called flexible optical solar reflector (OSR), having flexibility which is easily processed according to a surface shape of the airframe or a structure to be coated, is paid attention as the thermal-control material.
PTL 1 discloses a flexible thermal-control material including a metal layer on a polyimide film. In PTL 1, the surface of the polyimide film is subjected to roughening treatment, and accordingly secondary reflection of solar light is prevented and reflectivity and diffuseness are improved.